Floored Caverns

Cave System

Cave opening into Floored Caverns

Floored Caverns 2

Lava Caverns

with Cave Biome Size set to ExtraLarge

Better Caves with Quark

Better Caves with Quark, Thaumcraft, and Botania

Type 1 Caves

Showing Lava Cavern (red) and Floored Cavern (gold) Generation

Underground River

Underground Ocean

Better Caves Configuration

So many buttons!

Another set of steps bodes well; probably one of my favourite natural formations.

Taken by /u/ExtraBodybuilder

A little water and lava mixing.

Taken by /u/ExtraBodybuilder

A reflecting pool, deep underground.

Taken by /u/ExtraBodybuilder

Water caverns in 1.14.4

Underwater lake in 1.14.4

:0

Big Boi Caverns

Caverns configured with a huge size, featuring Underground Biomes and Quark

A Deep Chasm